This invention applies to the field of hydrodynamics, and relates to the use of gas cavities to reduce the frictional drag of hydrofoil craft, ship hulls and underwater surfaces in general. Using cavities to reduce frictional drag is covered in U.S. Pats. No. 3,077,173 (1963) and No. 3,109,495 (1963) for base-vented and side-vented hydrofoils, U.S. Pat. No. 3,205,846 (1965) for torpedoes, and U.S. Pat. No. 6,167,829 (2001), together with a pending continuation of that patent, for submerged surfaces in general.
The reduction of frictional drag provides basic benefits: power is reduced, and fuel consumption is reduced. These benefits reduce the weight of a vessel, which further reduces power and fuel consumption compared with a fully wetted vessel designed for a given payload and range. Alternatively, vessel speed can be significantly increased with the same displacement, power, payload and range. Cost and time for payload delivery are greatly reduced by reducing drag.
The problem is how to design underwater surfaces to make full use of cavities to reduce drag. Needs exist for improved drag reduction in water craft.